Expression of six cadherin molecules, E-, P-, N-cadherin, cadhelin-6,-11, and -13, in renal cell carcinomas (RCC), was investigated in order to elucidate whether these molecules are involved in the progression. Northern blot analysis of seven RCC cell lines showed that N-cadherin and cadhelin-6 were strongly expressed in all and 5 lines, respectively, whereas E, and P-cadherin were not detected at all. In KU2 cells transplanted to SCID mice, N-cadherin and cadhelin-6 were detected faintly in the subcutaneous tumors, but not in the metastatic tumors. Each cadherin expression in 30 surgically resected RCC was examined by immunostaining using frozen sections. The number of tumors expressing E-cadherin was significantly smaller than that of N-cadherin or cadhelin-6 (p<0.005). High grade tumors tended to have neither E-cadherin nor cadhelin-6 expression. In five metastatic tumors to the lung, cadhelin-6 was expressed in all, N-cadherin in 4, but E-cadherin in one. Using paraffin-embedded specimens of surgically resected RCC, expression of E- and N-cadherin was also examined immunohistochemically, and correlation between pathological tumor extension (pT classification) and the cadherin expression was analyzed. The patterns of each cadherin expression were almost the same as those in the aforementioned frozen specimens. In 10 primary tumors having metastatic lesions, N- and E-cadherin were detected in 8 and 4, respectively, and coexpression of E- and N-cadherin was observed in 3 tumors. High pT tumors tended to have N-cadherin expression. These results suggested that expression of N-cadherin or cadhelin-6, and absence of E-cadhelin expression might be correlated to the progression of RCC, although further studies will be necessary to draw. A conclusion